This invention relates to a method and apparatus for removing dust from the cell cores of pieces of honeycomb core material in preparation for bonding the core between sheets of material to form a honeycomb sandwich structure.
Honeycomb core is widely used in the preparation of panels and other parts fabricated of composite material for lightness and strength. The honeycomb core itself is a construction of mat or sheet material, such as aluminum, fiberglass, Kevlar, graphite or Nomex, which is glued or otherwise bonded on offset bond lines on every other sheet and then expanded to form a block of hexagonal cell material. The expanded block of honeycomb core material, if made of fiberous mat, can be impregnated with phenolic resin or the like and cured to form a stiff and light weight core structure for the honeycomb sandwich composite panel or part.
A typical honeycomb core composite panel or part is made by cutting a honeycomb core block across the cell columns, usually by a band saw, to make a flat slab on the order of 1-4 inches thick. If required for the shape of the part, the slab is shaped by milling and/or sanding to provide the correct cross sectional shape of the part. A composite sheet or skin is bonded to both sides of the honeycomb core to make the front and back faces of the part, and the edges are finished to complete the part.
The sawing, milling, and sanding operations on the honeycomb core part produce large quantities of dust which tend to collect in the hexagonal cell columns in the honeycomb core. Most of this dust falls out when the part is tapped against the work table, but a substantial portion remains adhering to the interior walls of the hexagonal cell columns by static electricity and simple adhesion to the interior cell walls.
In order to reduce the weight of the part, but primarily to insure good bonding of the front and back sheets to the core, the core must be thoroughly cleaned of dust which is generated in the shaping operations. In the past, the dust was vacuumed from the cell columns where the shaping operation occurred but a sizable quantity of dust remained on the interior cell walls. To remove this remaining dust, it has been necessary in the past to blow air through the core cell columns with a hand held air hose or draw air through the cell columns with a hand held vacuum hose, but the time and expense of hand operations of this nature are expensive and the completeness of dust removal was always somewhat haphazard. Moreover, the manual processes tend to spread the dust into the general shop atmosphere causing discomfort and general dissatisfaction among the shop personnel with the shop conditions, as well as substantially increasing the clean up requirement. Also, equipment operated in a dusty environment tends to collect the dust in the moving parts of the equipment and shortens their working life. Finally, it is believed that a clean shop environment tends to encourage clean working practices among the workers and demonstrate the employer's commitment to provide a clean and safe environment for the workers. For these and other reasons, it is highly desirable to provide a contained system for removing as much as is reasonably possible of the dust generated in the cutting and shaping operations on the honeycomb core parts, so as to keep the shop atmosphere as free as possible from free floating dust.